Optimization of automatic gain control for narrow bandwidth operation

ABSTRACT

The gain of an amplifier in a receiver operating in a cellular communication system is controlled by determining one or more gain variability metrics, which are then used to produce first and second threshold values. A frequency difference between a current carrier frequency and a target carrier frequency is ascertained and then compared to the threshold values. Target gain setting production is based on comparison results: If the frequency difference is larger than the first threshold, a first automatic gain control algorithm is performed; if the frequency difference is smaller than the first threshold and larger than the second threshold, a second automatic gain control algorithm is performed, wherein the second automatic gain control algorithm uses a current gain setting as a starting point; and if the frequency difference is smaller than both the first and second thresholds, the current gain setting is used as the target gain setting.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a § 371 national stage of PCT/EP2016/057872, filedApr. 11, 2016, which claims the benefit of U.S. Provisional ApplicationNo. 62/148,952, filed Apr. 17, 2015, and which also claims the benefitof U.S. application Ser. No. 14/825,141, filed Aug. 12, 2015 (issued onJul. 25, 2017 as U.S. Pat. No. 9,716,521) which applications are allhereby incorporated herein by reference in their entireties.

BACKGROUND

The present invention relates to Automatic Gain Control (AGC) in a radioreceiver, and more particularly technology that optimizes AGC inscenarios in which only a portion of a full transmission bandwidth isreceived at a time.

One of the most important properties of a hand held device is itsbattery life. For a User Equipment (UE) in a mobile communicationsystem, the dominating power consumer is the radio. In some cases, aUE's radio circuitry can be responsible for more than 50% of the totalpower consumption. Thus, minimizing the amount of time the radio needsto be active is crucial for extending the UE battery life.

Due to the limited dynamic range of the receiver, the UE needs to adjustthe gain prior to reception. An AGC algorithm, responsible for thisadjustment, typically starts by setting one or more amplifiers tooperate at some initial gain value. The power of the received signal isthen measured, and the gain is adjusted accordingly. This procedure isthen repeated until a good gain value has been found. If a good initialguess is available, the algorithm typically requires less radio time toconverge. Because the gain has to be corrected prior to reception ofuseful data, one must know how long the AGC algorithm needs to achieveconvergence so that reception can be started at the correct time. Thus,to be able to reduce the additional time needed prior to reception, onemust know a priori that an optimized algorithm can be used; otherwise,the worst-case time to convergence must be assumed. In some situationsit might even be possible to use a gain value from a previous run of theAGC algorithm.

AGC algorithms generally consist of three steps: power measurement, gaincomputation, and actuation. The purpose of the power measurement step isto estimate the received power of the signal. In the gain computationstep, a suitable gain value is determined; and in the actuation step,this gain value is applied to the receiver chain.

To be able to make a reliable estimate, the signal on which the estimateis based needs to be representative of the signal one wants to receive.For example in the case of Evolved Universal Terrestrial Radio Access(E-UTRA), some subframes might be allocated to Multimedia Broadcast overSingle Frequency Network (MBSFN) transmissions, or in the case of TimeDivision Duplex (TDD) mode, might be allocated for uplink transmission.In each of these examples, these subframes are not representative of thewanted signal and thus are not suitable for power measurements. Forexample, MBSFN subframes might be used by the Evolved NodeB (eNB) forpower saving purposes and thus contain no or at least very little powercompared to subframes allocated for regular downlink transmissions. Evenif all cells are not synchronized in time, the received power might bedominated by a nearby eNB. Thus the received power during MBSFNsubframes might be very low compared to regular subframes. It willfurther be recognized that subframes allocated for uplink transmissioncannot be used to estimate the power of downlink subframes. Thus, the UEmust limit power measurements to certain suitable time intervals. Thisis has the unwanted effect that the AGC procedure can be quite timeconsuming.

FIGS. 1 and 2 illustrate the limited time available for making suitablepower measurements for the cases of Frequency Division Duplex (FDD) andTDD operation, respectively. In the figures, in addition toabbreviations already introduced, the following abbreviations are used:

-   -   P-SCH: Primary Synchronization Channel    -   S-SCH: Secondary Synchronization Channel    -   TX: transmission    -   GP: Guard Period    -   UL: uplink

More particularly, FIG. 1 depicts synchronization signals and referencesymbols transmitted in an FDD cell. Only the central 72 sub-carriers areshown. Some sub-frames may be used for MBSFN, to take one example, andhence might not contain cell-specific reference symbols other than inthe first symbol.

FIG. 2 depicts synchronization signals and reference symbols transmittedin a TDD cell. Only the central 72 sub-carriers are shown. Somesub-frames may be used for UL transmissions and hence might not containcell-specific reference symbols, while others may be used for downlink(DL) transmissions but used for MBSFN transmissions, and hence containreference signals only in the first symbol.

During the actuation phase of the typical AGC algorithm, the gain valueis typically changed in multiple places through the receiver chain.These changes impair the received signal with, for example DC-transientsand phase discontinuities. Thus gain changes should be limited tomoments in time at which the impact of these impairments will be limited(i.e., they will not degrade reception of data). In the case of E-UTRAchannel reception, these changes can for example be limited to occur atslot or subframe borders.

A measure of the frequency channel variations is the so called coherencebandwidth, B_(c)≈1/τ_(max) where τ_(max) is the maximum delay spread(difference between the first and last significant tap in the impulseresponse). The coherence bandwidth for the three typical channelprofiles (i.e., Extended Pedestrian A (EPA), Extended Vehicular A (EVA)and Extended Typical Urban (ETU)) used in 3GPP are 2.44 MHz, 0.40 MHzand 0.2 MHz. Exemplary frequency responses for these three channels areillustrated in respective FIGS. 3a, 3b, and 3c for the case of a 20 MHzcell in good coverage conditions.

As a comparison, FIG. 4 illustrates the frequency response for a 3GPPETU channel for a 20 MHz cell in low coverage conditions (−10 dB SNR).

Conventional receiver equipment applies a “better safe than sorry”approach with respect to AGC. That is, the AGC is always scheduled torun, regardless of whether it is really needed. This conservativeapproach results in unnecessarily high power consumption under somecircumstances.

SUMMARY

It should be emphasized that the terms “comprises” and “comprising”,when used in this specification, are taken to specify the presence ofstated features, integers, steps or components; but the use of theseterms does not preclude the presence or addition of one or more otherfeatures, integers, steps, components or groups thereof.

Moreover, reference letters are provided in some instances (e.g., in theclaims and summary) to facilitate identification of various steps and/orelements. However, the use of reference letters is not intended toimpute or suggest that the so-referenced steps and/or elements are to beperformed or operated in any particular order.

In accordance with one aspect of the present invention, the foregoingand other objects are achieved in technology for controlling gain of anamplifier in a receiver operating in a cellular communication system.Gain control includes ascertaining a frequency difference between acurrent carrier frequency and a target carrier frequency and comparingthe frequency difference to a first threshold value. In response tosatisfaction of first criteria that include the frequency differencebeing larger than the first threshold value, a full automatic gaincontrol algorithm is performed to produce a target gain setting. Inresponse to satisfaction of second criteria that include the frequencydifference being smaller than the first threshold, an optimizedautomatic gain control algorithm is performed to produce the target gainsetting. The target gain setting is then used to control gain of theamplifier.

In an aspect of some but not necessarily all embodiments, the secondcriteria further include the frequency difference being larger than asecond threshold value.

In an aspect of some but not necessarily all embodiments, gain controlcomprises using one or more gain variability metrics to produce thesecond criteria.

In an aspect of some but not necessarily all embodiments, gain controlfurther comprises using the current gain setting as the target gainsetting in response to satisfaction of third criteria that include thefrequency difference being smaller than both the first and secondthresholds.

In an aspect of some but not necessarily all embodiments, the optimizedautomatic gain control algorithm uses a current gain setting as astarting point.

In an aspect of some but not necessarily all embodiments, gain controlcomprises determining one or more gain variability metrics.

In an aspect of some but not necessarily all embodiments, determiningone or more gain variability metrics comprises one or more of:

determining a current degree of coverage of the receiver;

determining whether the current carrier frequency and the target carrierfrequency are within a downlink system bandwidth of a same cell of thecellular communication system;

determining whether a source cell and a target cell are associated witheach other, wherein the source cell is transmitting on the currentcarrier frequency and the target cell is transmitting on the targetcarrier frequency; and

determining propagation conditions of a signal reaching the receiver.

In an aspect of some but not necessarily all embodiments, gain controlcomprises using one or more gain variability metrics to produce thefirst criteria.

In an aspect of some but not necessarily all embodiments, using the oneor more gain variability metrics to produce the first criteria comprisesusing a channel model and the one or more gain variability metrics toproduce the first criteria.

In an aspect of some but not necessarily all embodiments, using the oneor more gain variability metrics to produce the first criteria comprisesusing static information and the one or more gain variability metrics toproduce the first criteria.

In an aspect of some but not necessarily all embodiments, using the oneor more gain variability metrics to produce the first criteria comprisesascertaining whether historical gain variability data is available; andin response to historical gain variability data being available, usingthe historical gain variability data and the one or more gainvariability metrics to produce the first criteria.

In an aspect of some but not necessarily all embodiments, gain controlcomprises updating a database of historical gain variability data basedon one or more gain variability metrics.

In an aspect of some but not necessarily all embodiments, the databaseof historical gain variability data provides information indicating whatgain values have been used in the past when receiving data at one ormore particular frequencies.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the invention will be understood byreading the following detailed description in conjunction with thedrawings in which:

FIG. 1 depicts synchronization signals and reference symbols transmittedin an FDD cell.

FIG. 2 depicts synchronization signals and reference symbols transmittedin a TDD cell.

FIGS. 3a, 3b, and 3c depict exemplary frequency responses for threetypes of channels for the case of a 20 MHz cell in good coverageconditions.

FIG. 4 illustrates the frequency response for a 3GPP ETU channel for a20 MHz cell in low coverage conditions (−10 dB SNR).

FIG. 5 is, in one respect, a flow chart of steps/processes performed bycircuitry in accordance with some but not necessarily all exemplaryembodiments consistent with the invention.

FIG. 5A is, in one respect, a flow chart illustrating one or more of thesteps/processes/circuitry of FIG. 5 in more detail.

FIG. 6 is a block diagram of an exemplary embodiment of a deviceconsistent with the invention.

DETAILED DESCRIPTION

The various features of the invention will now be described withreference to the figures, in which like parts are identified with thesame reference characters.

The various aspects of the invention will now be described in greaterdetail in connection with a number of exemplary embodiments. Tofacilitate an understanding of the invention, many aspects of theinvention are described in terms of sequences of actions to be performedby elements of a computer system or other hardware capable of executingprogrammed instructions. It will be recognized that in each of theembodiments, the various actions could be performed by specializedcircuits (e.g., analog and/or discrete logic gates interconnected toperform a specialized function), by one or more processors programmedwith a suitable set of instructions, or by a combination of both. Theterm “circuitry configured to” perform one or more described actions isused herein to refer to any such embodiment (i.e., one or morespecialized circuits alone or in combination with one or more programmedprocessors). Moreover, the invention can additionally be considered tobe embodied entirely within any form of nontransitory computer readablecarrier, such as solid-state memory, magnetic disk, or optical diskcontaining an appropriate set of computer instructions that would causea processor to carry out the techniques described herein. Thus, thevarious aspects of the invention may be embodied in many differentforms, and all such forms are contemplated to be within the scope of theinvention. For each of the various aspects of the invention, any suchform of embodiments as described above may be referred to herein as“logic configured to” perform a described action, or alternatively as“logic that” performs a described action.

To illustrate various aspects of the inventive technology, parts of thisdescription take as their main focus, scenarios in which a Machine TypeCommunication (MTC) device operates within a given cell bandwidth buttunes its receiver to only parts of the transmission bandwidth at anygiven time, and thus needs to retune its receiver to receive other partsof the transmission bandwidth of the cell. Thus the carrier frequency isonly slightly changed between receptions. This is different compared tocases in which inter-frequency measurements (potentially on a differentband) need to be performed.

Notwithstanding this focus, the invention is not limited to use only inMTC devices, but is usable under any circumstances in which itsapplication would prove beneficial.

In one aspect, embodiments consistent with the invention take advantageof the fact that, if the carrier frequency is changed only slightly andwithin the DL system bandwidth of the cell hosting the device, the AGCprocedure can be optimized. The optimized procedure can be done insteps, with the degree of optimization being determined based on thedistance between the current and target carrier frequencies and/or thedegree of coverage.

These and other aspects will now be described in further detail.

In one aspect of embodiments consistent with the invention, an AGCscheduler implements an algorithm for selecting which of a number of AGCmethods to use at any given time, with selection being based on one ormore of the following:

-   -   whether a gain setting for the current carrier frequency (i.e.,        the one the receiver is presently tuned to) exists    -   the distance in frequency between the current carrier frequency        and the carrier frequency to which the receiver is to be tuned    -   the degree of coverage at the current carrier frequency (e.g.,        in terms of signal-to-noise ratio (SNR), signal-to-interference        ratio (SIR), and/or signal-to-interference plus noise ratio        (SINR) levels, which are indicative of whether the device is        operating in so-called enhanced coverage or normal coverage, as        these terms are known in the art of mobile communications). If        the device's degree of coverage is enhanced coverage, thermal        noise from the low-noise amplifier in the receiver dominates        over sources of interference (e.g., from neighboring cells).        Under these conditions, the same gain setting as is presently        being used can be assumed to apply to operation at the target        frequency as long as the device (e.g., MTC device) is operating        within the cell bandwidth of the serving cell. This is in        contrast to scenarios that, in general, are        interference-limited, whereby the gain setting for use at the        target frequency very much depends on whether the serving (and        intra-frequency neighbor) cells are empty or fully loaded in the        concerned subframe.    -   whether the source (current) and the target carrier frequencies        are within the DL system bandwidth of the same cell, for        example, a cell serving UEs over a wide bandwidth and also MTC        devices in narrow subbands    -   whether the source and target cells are associated with each        other; for example, collocated cells operating in intra-band        contiguous Carrier Aggregation (CA) (Primary Cell—PCell—and one        or more Secondary Cells—SCells) for UEs supporting the feature,        and for which a fixed power offset can be assumed, or other        collocated cells, for example, operating on one carrier        frequency for broadcast and multicast and another carrier for        unicast    -   the expected amount of channel variability with respect to        frequency and degree of coverage based on previous receptions or        other a priori information

Another aspect of some embodiments consistent with the invention is theuse of a Variability Database that stores historical data regarding gaindifferences for different frequencies at different degree of coverage.

These and other aspects will now be described with reference to FIG. 5,which is, in one respect, a flow chart of steps/processes performed bycircuitry in accordance with some but not necessarily all exemplaryembodiments consistent with the invention. In another respect, FIG. 5can be considered to depict exemplary means 500 comprising the variousillustrated circuitry (e.g., hard-wired and/or suitably programmedprocessor) configured to perform the described functions.

The functionality depicted in FIG. 5 is invoked when the device isrequested to tune its receiver from a current frequency, f1, to a nearbyfrequency, f2. In one step, the circuitry ascertains whether there areexisting gain settings for the current carrier frequency, f1 (decisionblock 501). If not (“No” path out of decision block 501), it isnecessary to perform a full (i.e., non-optimized) AGC algorithm, soprocessing continues at step 513 for this purpose.

If there are existing gain settings for the current carrier frequency,f1 (“Yes” path out of decision block 501), then further processingdetermines whether these can be used as a basis for running an optimizedAGC algorithm. As part of that further processing, one or more gainvariability metrics are determined (step 503). Exemplary gainvariability metrics include, but are not limited to, the following:

-   -   The magnitude of the frequency difference |f2−f1| (e.g., in Hz)        between the current (source) frequency and new (target)        frequency (f2)    -   The device's current degree of coverage. In some embodiments,        this can be ascertained directly (e.g., from network signaling,        which can be dedicated signaling directed to the device or        alternatively broadcast to devices within a coverage area).        Alternatively, the device's current degree of coverage can be        ascertained indirectly. Indirect indicators of whether the        device is operating in so-called enhanced coverage or normal        coverage, as these terms are known in the art of mobile        communications, include, but are not necessarily limited to:        measured Reference Signal Received Power (RSRP), SNR, SIR,        and/or SINR levels. Using these types of measures, the device        can assess whether the wanted signal is well below the noise        floor, which is an indicator that the device is in enhanced        coverage conditions. If the wanted signal is well above the        noise floor, the device is operating in normal coverage        conditions, in which case channel variations must be taken into        account.    -   Whether the source and the target carrier frequencies are within        the DL system bandwidth of the same cell.    -   Whether the source and target cells are associated with each        other. An exemplary association is the case of collocated cells        having a fixed power offset with respect to one another.    -   Propagation conditions, where for example pronounced multipath        propagation may be indicative of fading dips in particular parts        of the spectrum.

Any one or combination of the above can be used to ascertain the extentto which current gain settings can be used either “as is” or at least asa starting point for determining gain settings for operation at thetarget carrier frequency.

Next, the device ascertains whether there is historical gain variabilitydata available for the carrier frequencies f1 and f2 (decision block505). The historical gain variability data is a record indicating thetypical difference in gain that the device has used when receiving onthe frequencies f1 and f2 in the past for different degrees of coverage.

If no such historical data is available (“No” path out of decision block505), default (conservative) criteria (e.g., one or more thresholdvalues) are derived based on typical channel models or other static, apriori information (step 507). But if historical gain variability datais available (“Yes” path out of decision block 505), then this is usedto generate criteria (e.g., one or more threshold values) that arebetter tailored to the device's actual operating conditions (step 509).

Regardless of whether they are generated from default information orfrom historical data, the threshold values generated by steps 507 and509 constitute thresholds that represent when one AGC mode should beused over another for a given difference between the frequencies f1 andf2. In this respect, the gain variability metrics determined in step 503influence what thresholds will be generated in either of steps 507 and509.

Next, the generated criteria (thresholds) are used as a basis forselecting how to generate gain settings for the device (step 511). Moreparticularly, and as illustrated in greater detail in FIG. 5A, step 511in at least some exemplary embodiments comprises ascertaining thefrequency difference between the source (current) carrier frequency, f1,and the target carrier frequency, f2 (step 551). The ascertainedfrequency difference is then compared (step 553) with the criteria(thresholds) generated from one of the steps 507 and 509. If thefrequency difference is larger than a first threshold, this means thatthe frequency difference is large compared to the channel variations;consequently, a robust AGC mode (“full AGC”) that does not rely on anyassumptions regarding the received power is used (step 513).

If, in the comparison illustrated by decision block 553, the frequencydifference is smaller than the first coverage dependent threshold but is(at least in some embodiments) larger than a second threshold, then thefrequency difference is deemed to be quite small compared to the channelvariations. Consequently, an optimized AGC algorithm is used to derivegain values, with the optimization arising from the use of the existinggain settings for operation at frequency f1 as a starting point (step515).

Still considering step 511, and more particularly the comparisonillustrated by decision block 553, if the frequency difference issmaller than the second coverage dependent threshold, then the frequencydifference is deemed to be small compared to the channel variations(i.e., small compared to the coherence bandwidth—the bandwidth overwhich the frequency characteristics of the channel can be approximatedto be constant), then AGC is not used at all. Instead, the current(stored) gain settings for operation at frequency f1 are applied for useat the target frequency f2 (step 517).

Having generated gain settings by one of the steps 513, 515, and 517,they are applied to the receiver (i.e., to control amplifier gain asillustrated by step 518) and data reception begins (step 519), and thegain is updated continuously to track channel variations.

As this embodiment relies on historical gain variability data, it isadvantageous to make that data as complete as possible. Thus, the gainvariability data is updated for the frequencies f1 and f2 to improvefuture decisions.

The following examples illustrate how gain values can be generated inaccordance with an exemplary embodiment consistent with the invention:

Example 1

Assume that Metrics={|f2−f1|=5 MHz, normal coverage}, and historicaldata exist for these metrics. Consequently, thresholds are generatedbased on historical data and an optimized AGC algorithm is performed.

Example 2

Assume that Metrics={|f2−f1|=5 MHz, normal coverage}, and no historicaldata exists for these metrics. Consequently, thresholds are generatedbased on a model, and a full AGC algorithm is performed.

Example 3

Assume that Metrics={|f2−f1|=5 MHz, extended coverage}, and historicaldata exist for these metrics. Consequently, thresholds are generatedbased on historical data, and the stored gain currently being used forreception at frequency f1 is applied for use at frequency f2 withoutperforming any AGC algorithm.

FIG. 6 is a block diagram of an exemplary embodiment of a device 600consistent with the invention. The device comprises an analog RFfront-end 601, as is known in the art. The analog RF front-end 601includes, among other circuitry, at least one amplifier, as illustratedin this example by the amplifier 603. The analog RF front-end 601 istuned to a given carrier frequency, and receives a signal. The analog RFfront-end outputs the received analog signal to an analog-to-digitalconverter (ADC) 605, which generates therefrom a digital form of thesignal. The digital received signal is supplied to digital baseband (BB)circuitry 607, which processes the signal to receive therefrom theintended received data.

As described above, it is important for good data reception that thegain of the amplifier 603 be properly adjusted. For this purpose, thedigital received signal supplied at the output of the ADC 605 is alsosupplied to AGC circuitry 609 which generates and supplies gain valuesto a gain control input of the amplifier 603. In an aspect of thisembodiment, the AGC circuitry 609 is able to selectively perform any oneof full and optimized AGC algorithms. Selective control of the AGCcircuitry 609 is also able to make it not run any algorithm at all, andinstead to simply pass along a current gain setting (being used foroperation at a current/source carrier frequency) for use at a new,target carrier frequency. Although this last option has been describedas an affirmative action performed by the AGC circuitry 609, it will berecognized that in some embodiments the AGC circuitry 609 need notactually do anything to bring about the desired result, since theamplifier 603 is already operating at the desired (current) gainsetting.

Selective operation of the AGC 609 is controlled by a scheduler 611,which is configured to carry out methodology consistent with theprinciples described herein, such as with reference to FIG. 5. Thescheduler 611 is therefore coupled to the AGC 609, thereby enabling thescheduler 611 to provide one or more control signals to the AGC 609, andalso (in some embodiments), to receive information from the AGC 609,such as present gain setting information.

In this illustrated embodiment, the scheduler 611 is also coupled to anontransitory memory 613, at least for storing and making available data615, such as gain variability data as described earlier.

The scheduler 611 can be embodied in any number of forms, such asprogrammable alone or in combination with other circuitry 617. Whenprogrammable processor is used, the memory 613 can further store programdata 619 configured to cause the processor to carry out AGC controloperations, such as those described above with reference to FIG. 5.

In this illustrative embodiment, the memory 613 has been shown as anentity that is separate from the scheduler 611. However, this is not arequirement; in alternative embodiments, the scheduler 611 can, itself,include one or more memory devices.

To further illustrate aspects of embodiments consistent with theinvention, an example will now be described that applies principlesdescribed above. Assume that a low-cost MTC device, capable ofsupporting a bandwidth spanning only 6 resource blocks (RBs) (i.e., 1.4MHz), is hosted by a cell having 100 RBs (20 MHz) DL system bandwidth.The device is allocated a subband comprising 6 RBs in a part of thespectrum, outside the central 6 RBs, for unicast communication. Thedevice regularly needs to retune to the central 6 RBs to search forsynchronization signals and to perform RSRP measurements onintra-frequency neighbor cells. The MTC device thus repeatedly hops backand forth between groups of RBs (each being 6 RBs wide) within the DLbandwidth of the hosting serving cell.

When hopping within the same cell, the power level of the referencesignals in the target subband (i.e., the central 6 RBs) is known fromearlier operation in this part of the spectrum; hence, the device has agood idea about expected gain variation when returning to the targetsubband and can avoid carrying out a gain search and instead directlyapply, for example, the same analog gain setting that was used for thesource subband.

When operating in complex radio conditions with fading, the frequencycharacteristics of the radio channel may vary over the DL systembandwidth. In such instances, the larger the distance between source andtarget subbands the more the characteristics of the radio channel maydiffer. As a result, when significant fading is detected the device mayapply a more conservative approach and search/adjust the gain beforeattempting to receive a signal in the target subband. This is because itis known from historical data that even a quite small frequency changemight result in large gain changes; consequently, just using the gainsetting being applied at the source (current) frequency will not work.The historical data does not directly contain which gain to use for acertain frequency, but rather indicates how much variation can beexpected.

Various aspects of the herein-described technology provide advantagesover conventional AGC techniques. For example, by detecting when anoptimized AGC procedure can be used (or even when current gain settingscan be applied “as is” for a target frequency), devices avoidunnecessarily spending time and power to arrive at gain settings.

The invention has been described with reference to particularembodiments. However, it will be readily apparent to those skilled inthe art that it is possible to embody the invention in specific formsother than those of the embodiment described above. The describedembodiments are merely illustrative and should not be consideredrestrictive in any way. The scope of the invention is furtherillustrated by the appended claims, rather than only by the precedingdescription, and all variations and equivalents which fall within therange of the claims are intended to be embraced therein.

The invention claimed is:
 1. An apparatus for controlling gain of an amplifier in a receiver operating in a cellular communication system, the apparatus comprising: circuitry configured to select and then perform an automatic gain control algorithm from among a plurality of automatic gain control algorithms, wherein the circuitry configured to select and then perform comprises: circuitry configured to ascertain a current carrier frequency to which the receiver is currently tuned and a target carrier frequency to which the receiver is requested to tune; circuitry configured to perform a first automatic gain control algorithm to produce a target gain setting for the amplifier in response to a determination that the current carrier frequency and the target carrier frequency are not within a downlink system bandwidth of a same cell of the cellular communication system; circuitry configured to perform a second automatic gain control algorithm to produce the target gain setting for the amplifier in response to a determination that the current carrier frequency and the target carrier frequency are within the downlink system bandwidth of the same cell of the cellular communication system; and circuitry configured to use the target gain setting to initially control gain of the amplifier when the receiver is tuned to the target carrier frequency.
 2. A receiver comprising an amplifier; and the apparatus of claim 1 arranged to control the amplifier.
 3. A User Equipment (UE) device comprising the receiver of claim
 2. 4. The User Equipment device of claim 3 wherein the User Equipment device is a Machine Type Communication (MTC) device. 